1. Field of the Invention
The present invention relates to a hose for transporting a fluid, specifically a hose with elastic sealing layer for transporting a fluid, which is suitable for a hose for transporting a fuel in a motor vehicle or the like, and relates to a method for producing the same.
2. Description of the Related Art
Typical rubber hoses have been used conventionally for transporting a fuel in motor vehicles in view of high vibration-absorbability, easy assembling or the like. Such rubber hoses are, for example, made of a blend of acrylonitrile butadiene rubber and polyvinyl chloride (NBR/PVC) that is excellent in permeation resistance to gasoline. However, for the purpose of global environment protection, the regulations have been recently tightened against permeation of a fuel for motor vehicles or the like, and are anticipated to be further tightened in the future.
In order to provide a hose for transporting a fuel of a motor vehicle with permeation resistance to a fuel, the hose is configured such that a hard resin layer having permeation resistance to a fuel is laminated and formed on an inner side of a tubular hose body made of an elastic material such as rubber. The hard resin layer serves as a barrier layer against permeation of a fuel.
Although such type of the hose has been proposed and used conventionally, as the resin layer having permeation resistance to a fuel is made of hard material, when a rigid mating pipe such as a metal pipe is fitted directly in an inner surface of the resin layer, a sealing property becomes insufficient between the mating pipe and the hose for transporting a fuel, specifically the resin layer on an inner surface of the hose. And, in order to fit the mating pipe into an opening of an axial end of the hose, a great force is required, and this causes a problem that workability (workability is a property regarding to the ease with that the mating pipe is fitted in the hose) is deteriorated.
Under the circumstances, a connecting structure as shown in FIG. 5 (A) is previously proposed (Patent Document 1, below).
In FIG. 5 (A), reference numeral 200 indicates a hose for transporting a fuel (hereinafter simply referred to as a hose), reference numeral 202 indicates a tubular hose body made of rubber, reference numeral 204 indicates a hard resin layer as a permeation barrier layer laminated and formed on an inner surface of the tubular hose body 202. The resin layer 204 has permeation resistance to a fuel.
Here, the resin layer 204 is laminated and formed on the inner surface of the tubular hose body 202 up to an axial end of the tubular hose body 202 or the hose 200.
In this connecting structure, a connecting end portion 212 of the hose 200, which is connected to a rigid mating pipe 208 as shown in FIG. 5 (B), is provided with a long tubular sealing rubber 206 having permeation resistance to a fuel on an inner surface thereof. The sealing rubber 206 is formed or molded on an inner surface of the resin layer 204 in the connecting end portion 212, and then is vulcanized and adhered integrally to the inner surface of the resin layer 204. The mating pipe 208 is fitted in the resin layer 204 via the sealing rubber 206. The mating pipe 208 and the resin layer 204 are fitted to each other via the sealing rubber 206.
In this connecting structure, compared to a connecting structure in which the mating pipe 208 is inserted directly in the resin layer 204, sealing property is good, and workability of fitting of the mating pipe 208 in the hose 200 is improved.
However, in the hose connecting structure as shown in FIG. 5 (A), as the sealing rubber 206 is made of an expensive material that has permeation resistance to a fuel, the hose 200 costs high.
Patent Document 2 below discloses a connecting structure in which this problem is improved.
FIGS. 5 (B) and (C) show this specific example.
As shown in FIG. 5 (B), in this connecting structure, an annular recessed part 214 is formed in an inner surface of the resin layer 204 near or toward a leading end thereof, an elastic sealing ring 216 having permeation resistance to a fuel is fitted in the annular recessed part 214, and the mating pipe 208 is fitted or disposed in an inner surface of the elastic sealing ring 216 in contact relation.
Here, the mating pipe 208 is provided with an annular bulged portion 210 bulged radially outwardly on a leading end portion of an inserting side thereof. The bulged portion 210 bites in an inner side of the elastic sealing ring 216 so as to elastically compress the elastic sealing ring 216 radially outwardly.
Meanwhile, in an inner surface of the hose 200, a raised portion raised downwardly in the figure, namely raised radially inwardly is formed. The raised portion abuts the leading end portion of the mating pipe 208 in the axial direction and thereby defines a fit-in length of the mating pipe 208. Namely, the mating pipe 208 relatively fits in the hose 200 until the leading end portion abuts the raised portion
In FIGS. 5 (B) and (C), reference numeral 220 indicates a clamp member, and the connecting end portion 212 of the tubular hose body 202 is fastened on an outer surface thereof by the clamp member 220 in a diametrically contracting direction, and securely fixed to the mating pipe 208, namely clamped to the mating pipe 208.
In the connecting structure in FIGS. 5 (B) and (C), the elastic sealing ring 216 is attached in the annular recessed part 214 in fit-in relation in a following manner.
FIG. 6 illustrates this manner concretely.
In FIG. 6 (A), reference numeral 222 indicates an attachment jig for the elastic sealing ring 216. The attachment jig 222 has a rod portion 224 and a disk-like press portion 226 on a leading end portion thereof.
Here, the press portion 226 includes a tapered surface 228 on a left side thereof in the figure, namely on a front surface side.
The attachment jig 222 also has a holder portion 230 on a left side in the figure, namely on a leading end with respect to the press portion 226. The holder portion 230 includes an outer periphery shaped in a figure “8”.
Here, the elastic sealing ring 216 is deformed and held in the shape of the figure “8” on the holder portion 230. The attachment jig 222 is pushed and inserted in the connecting end portion 212 while diametrically expanding the connecting end portion 212 of the hose 200 by the disk-like press portion 226. At the time when the elastic sealing ring 216 reaches a position of the annular recessed part 214, the elastic sealing ring 216 held on the holding portion 230 is released from the holder portion 230 to seat in the annular recessed part 214 by rotating the attachment jig 222. Thereby the elastic sealing ring 216 is attached in the annular recessed part 214.
In the connecting structure shown in FIGS. 5 (B) and (C), a cost of material required for the elastic sealing ring 216 is low, as usage of the material is less, compared to that for the sealing rubber 206 in the connecting structure as shown in FIG. 5 (A). However, as the elastic sealing ring 216 is a molded article or molded part similarly to the sealing rubber 206 shown in FIG. 5 (A), there is a following problem in the elastic sealing ring 216. Namely, a cost required for molding the elastic sealing ring 216 is high, and a separate or further step is required for attaching such elastic sealing ring 216 in the inner surface of the connecting end portion 212 of the hose 200, specifically in the annular recessed part 214 in fit-in relation.
Further, this attachment step is complicated and accompanied by troubles. In addition, the elastic sealing ring 216 is shaped of a ring as its name suggests, and possibly is kinked during attachment. So, attachment of the elastic sealing ring 216 should be done successfully, and otherwise there is a fear of defective attachment.
Thus, there is also a problem that an inspection step following the attachment step is essential for inspecting whether the elastic sealing ring 216 is attached correctly in a predetermined location and attached in a correct attachment form. So, this involves a problem that an overall cost for connecting procedure including the attachment step and the inspection step is still not low sufficiently.
The above explanation is given, taking a hose for transporting a fuel as an example. However, this problem could occur in common to such hose as includes an inner layer of resin as a barrier layer having permeation resistance to a fluid transported in order to restrain the fluid transported from permeating.                [Patent Document 1] JP-A, 8-294979        [Patent Document 2] JP-A, 2002-54779        
The present invention is made under the foregoing circumstances. It is an object of the present invention to provide a hose for transporting a fluid that requires low cost for a structure for connection to a mating pipe, and to provide a method for producing such hose for transporting a fluid.